EBOLA is back. As of April 14th the virus had infected 168 people in Guinea, in west Africa, according to the World Health Organisation (WHO). At least 108 have died. In neighbouring Liberia, six are known to have had the disease, with more cases suspected. Nearly 400 remain under observation. Airports are taking travellers' temperatures and Senegal's border with Guinea was closed. With a mortality rate of up to 90%, ebola is terrifying. Is it possible to contain an outbreak?

Humans have no immunity against the disease, which is thought to be native to bats. The virus is transferred in bodily fluids, most commonly blood. Once inside a host it incubates for between two days and three weeks before causing flu-like symptoms. With little to stop it, ebola attacks the whole body at once, triggering a cascade of immune responses that lead to haemorrhage, organ failure and often death. The virus was discovered in 1976 when two strains hit Sudan and what was then Zaire (now the Democratic Republic of Congo), infecting a total of 602 people and killing 431. The worst single outbreak hit Uganda in 2000, infecting more than 400 people, half of whom died. But until now the virus had never been seen as far west as Guinea or Liberia. Health-workers in Guinea did not recognise the disease at first.

Sudden and deadly though it is, ebola can be contained, for three reasons. The first is transmission: the virus is not airborne. It is transferred only through direct contact with someone who is visibly sick. "It's not that one person enters a bus, and half of the bus is infected," explains Dr Matthias Borchert of the London School of Hygiene and Tropical Medicine. Because the early symptoms of ebola resemble more common diseases, reported infections quickly grow. Following the recent outbreak, suspected cases were flagged in Ghana, Sierra Leone and Mali, before the patients later tested negative (a few results from Mali have not yet been returned). The second reason is preparation. The WHO, Médécins Sans Frontiers and ministries of health devote tremendous resources to building wards, isolating suspected patients and tracking their contacts. "Even basic precautions reduce the risk of transmission," says Barbara Knust of the Atlanta-based Centres for Disease Control and Prevention. Finally, ebola is treatable. Although no cure exists, the services available in an intensive care unit can help a patient beat the bug.

In any outbreak, rumours spread quickly, conspiracy theories are rife and bunk treatments proposed (a mixture of raw onions and Nescafé is one example currently doing the rounds). So reliable information is crucial. Banning travel and closing borders can push the disease underground; both are discouraged by the WHO. According to doctors, one new aspect of the Guinea outbreak has been patients' use of mobile phones, which makes isolation wards a bit less awful and provides succour to families, encouraging communities to work with health providers rather than against them. With a continued strong response, the current outbreak can be stopped before it becomes an epidemic.

- See more at: http://www.economist.com/blogs/economist-explains/2014/04/economist-explains-6#sthash.Zn8hYMM2.dpuf